u8500-charger: Delay for USB enumeration

u8500-charger: Delay for USB enumeration

If charging is started before USB enumeration of an Accessory
Charger Adapter has finished, the AB8500 will generate a
VBUS_ERROR. This in turn results in timeouts and delays the
enumeration with around 15 seconds. This patch delays the
charging and then ramps currents slowly to avoid VBUS errors.
The delay allows the enumeration to have finished before
charging is turned on.

Signed-off-by: Martin Sjoblom <martin.w.sjoblom@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Jonas ABERG <jonas.aberg@stericsson.com>
Tested-by: Jonas ABERG <jonas.aberg@stericsson.com>